A commonly used multi-axis industrial robot includes a mounting cover, a turning flange which turns around an axis over the mounting cover, and a robot arm which is mounted on the turning flange. A stopper is attached to the mounting cover and the turning flange for the purpose of mechanically limiting the operating angle of the turning flange when the rotation angle reaches a preset limit.
As shown in FIG. 1, a mechanical stopper is installed on the robot housing unit 1 of a rotary joint. A circular orbit 2 and a stop dog 5, which is further shown in FIG. 2, are installed on a cover 8, which is fixed on the robot body by bolts. A single slider 10, which is further shown in FIG. 3, is placed between the circular orbit 2 and a rotation flange 3. A bolt 4 is plugged in the rotation flange 3.
The problem of the foregoing existing technique is that the limit of the operating angle of the turning angle cannot be set to a value in the vicinity of or beyond ±360 degrees. More specifically, when the rotation flange 3 begins to rotate, the bolt 4 moves along with the flange 3. When the bolt 4 moves to the position against the slider 10, it pushes the slider 10 moves forward until they are obstructed by the stop dog 5. In this case, the rotation angle is 360 degrees-ω (ω is shown in FIG. 1). If the rotation flange 3 rotates in an opposite direction, the result is the same. Therefore, the rotation angle range for this mechanical stopper is ±(360−ω) degrees. That is, the operating angle of the turning flange 3 cannot be set to a value of 360 degrees or more. Further, even if the operating angle is set to a value less than 360 degrees, it is difficult to set the operating angle to a value close to 360 degrees.
Generally, limited by the cable performance and structure of mechanical stopper, the robot joint cannot rotate 360 degrees or more in a single direction. However, in some actual working applications, a wide-angle rotation, that is, a whole 360 degrees circle or more, is required by the robot joint. As a matter of course, elimination of the stopper can also be selected. However, in order to protect a drive cable or the like (not shown) of the robot arm connected between the mounting cover 8 and the turning flange 3, the operating angle of the turning flange 3 must be mechanically limited.
Therefore, there is a demand for a stopper capable of setting the limit of operating angle of the turning flange 3 to a value of ±360 degrees or more.